EP0179593A1 - Druckluftlose Sprühpistole mit Entladungsschutz für die Spitze - Google Patents

Druckluftlose Sprühpistole mit Entladungsschutz für die Spitze Download PDF

Info

Publication number
EP0179593A1
EP0179593A1 EP85307199A EP85307199A EP0179593A1 EP 0179593 A1 EP0179593 A1 EP 0179593A1 EP 85307199 A EP85307199 A EP 85307199A EP 85307199 A EP85307199 A EP 85307199A EP 0179593 A1 EP0179593 A1 EP 0179593A1
Authority
EP
European Patent Office
Prior art keywords
nozzle
tip
nozzle tip
spray gun
coating material
Prior art date
Legal status (The legal status is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the status listed.)
Granted
Application number
EP85307199A
Other languages
English (en)
French (fr)
Other versions
EP0179593B1 (de
Inventor
James J. Turner
Joseph C. Waryu
Current Assignee (The listed assignees may be inaccurate. Google has not performed a legal analysis and makes no representation or warranty as to the accuracy of the list.)
Nordson Corp
Original Assignee
Nordson Corp
Priority date (The priority date is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the date listed.)
Filing date
Publication date
Application filed by Nordson Corp filed Critical Nordson Corp
Publication of EP0179593A1 publication Critical patent/EP0179593A1/de
Application granted granted Critical
Publication of EP0179593B1 publication Critical patent/EP0179593B1/de
Expired legal-status Critical Current

Links

Images

Classifications

    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B05—SPRAYING OR ATOMISING IN GENERAL; APPLYING FLUENT MATERIALS TO SURFACES, IN GENERAL
    • B05B—SPRAYING APPARATUS; ATOMISING APPARATUS; NOZZLES
    • B05B5/00—Electrostatic spraying apparatus; Spraying apparatus with means for charging the spray electrically; Apparatus for spraying liquids or other fluent materials by other electric means
    • B05B5/025—Discharge apparatus, e.g. electrostatic spray guns
    • B05B5/035—Discharge apparatus, e.g. electrostatic spray guns characterised by gasless spraying, e.g. electrostatically assisted airless spraying

Definitions

  • This invention relates generally to apparatus for the airless atomization and electrostatic deposition of a coating material upon a substrate.
  • the invention more particularly concerns such an apparatus which includes an electrically conductive nozzle tip which acquires an electrical charge during operation of the apparatus.
  • One type of equipment often used includes a spray gun which atomizes and electrostatically charges the coating material, such as paint, as the material is applied to the substrate.
  • electrostatic coating guns normally provide either airless or air spray atomization of the coating material.
  • the electrostatic field produced by the electrode imparts a charge to the spray particles which causes the particles to be attracted to the substrate, which is typically grounded.
  • the charged atomized coating material is in effect drawn to the substrate, resulting in increased and more efficient deposition of the coating material.
  • Such airless spray guns often operate in an explosive environment. This is brought about by, for example, paint solvent vapours from the atomization of a solvent-containing paint. In such an environment it is imperative to prevent the creation of a high energy spark which might ignite solvent vapours or the like in the atmosphere.
  • the gun electrode is coupled to the high voltage supply through a high resistance path, usually including a final resistor near the gun nozzle itself. In this way, if the gun electrode is moved close to an electrical ground, there is insufficient energy at the electrode to support an arc due to the effective high impedance of the high voltage source.
  • the electrode, or antenna, itself extends beyond the end of the final series resistor in the gun, and is charged to a high voltage, the mass of the electrode is small. Therefore, the energy storage capacity of the electrode itself is insufficient to support an arc to an electrical ground adjacent the electrode. In practice, if the charged electrode is brought close to an electrical ground, there is a low energy corona discharge, but no arcing occurs.
  • an airless gun since the more metal there is in the nozzle, the greater the energy storage capability, it would be ideal to form the entire nozzle, other than the electrode, from a non-conductive material such as a plastic material.
  • a non-conductive material such as a plastic material.
  • the atomizing tip is subject to very rapid wear if constructed of a plastic material. Consequently, in almost all cases, an airless gun includes a metallic tip in the nozzle at which the atomization of the pressurized coating material occurs.
  • This metal gun tip is mounted in a substantially non-conductive nozzle assembly, electrically isolated from the high voltage electrode.
  • the gun tip is also electrically isolated from ground by virtue of being mounted within the non-conductive nozzle assembly.
  • the metal tip of the gun becomes electrostatically charged, primarily through conduction of electrical charge from the electrode to the tip via the atomized coating material emitted from the nozzle tip.
  • the electrostatically charged nozzle tip in turn, has sufficient mass and electrical charge storage capacity that an arc can be drawn from the nozzle tip to an adjacent electrical ground.
  • the electrode serves as a shield for the nozzle tip, preventing an electrical discharge from the nozzle tip in the form of an arc.
  • the gun tip is not so shielded and an arc may be produced.
  • This secondary electrode was not intended to have an effect upon the electrostatic field presented to the atomized coating material exiting from the nozzle tip. However, it has been found that, while the secondary electrode serves to cooperate with the primary electrode to adequately shield the nozzle tip, preventing arcing in the presence of an electrical ground, the secondary electrode has detracted from the coating material transfer efficiency of the gun. Apparently, the introduction of the secondary electrode has reduced the particle-charging effectiveness of the electrostatic field created by the primary electrode.
  • This objective has been accomplished in accordance with the invention by providing a resistive element in the gun nozzle having a first portion electrically coupled to the nozzle tip and a second, exposed portion positioned to serve as a shield for the gun tip.
  • the charging electrode is positioned above the nozzle tip and the two resistive threads are mounted about 90° apart below the nozzle tip. If the lower portion of the nozzle tip is moved adjacent an electrical ground, an arc is not drawn from the tip to the electrical ground, but instead there is a low energy corona discharge from one or both of the exposed ends of the resistive threads to the electrical ground.
  • the exposed ends of the resistive threads are positioned to be generally more closely adjacent an approaching electrical ground than the lower portion of the nozzle tip. This positioning provides for a low energy corona discharge of electrical energy on the nozzle tip through one or both of the resistive elements, preventing an arc from the nozzle tip to the electrical ground. In effect, the charge in the nozzle tip is drained away through the resistive threads as a grounded object approaches.
  • resistive threads are coupled to the electrostatically charged nozzle tip, they produce virtually no adverse effect upon the electrostatic field created by the charging electrode.
  • an airless spray system includes a gun 10 formed to be held in the hand of an operator.
  • the gun 10 need not be a hand held gun but could be of a type to be mounted upon a robot, or a platform, or the like and could be either fixed or movable.
  • articles (not shown) to be coated are generally conveyed past the gun.
  • the gun 10 includes a body portion 11, a handle 12, and a trigger 13.
  • a hose 14 connects the gun with a source 15 of coating material under high pressure, typically on the order of 300 to 1,000 psi.
  • An electrical power supply 18 is connected to the gun 10 by a cable 19.
  • the power supply 18 is coupled via the cable 19 through one or more resistors in the gun 10 to an electrode 20, which generates an electrostatic field to charge liquid coating material particles which are atomized by passage through a metal nozzle insert 26 mounted in a metal nozzle adaptor 27 ( Figure 2).
  • the structural details of the gun 10 relevant to the present invention reside in the forward end portion of the gun, as generally shown in cross-section in Figure 2.
  • the remainder of the gun rearwardly from this portion has not been illustrated in detail since it may be conventional, such as in the guns described in U.S. Patents No. 3,731,145 and No. 4,355,764, commonly assigned herewith.
  • the nozzle assembly 25 of the gun 10 includes the nozzle adapter 27 within which is mounted the nozzle insert 26.
  • the insert 26 is typically brazed within the nozzle adapter 27.
  • the nozzle adapter 27 and the nozzle insert 26 shall be commonly referred to herein as the nozzle tip.
  • the nozzle tip 26, 27 is mounted within a non-conductive nozzle support ring 28, and the nozzle tip and nozzle support ring together comprise the spray nozzle of the gun 10.
  • the support ring 28 is held in place by a non-conductive sealing plug 29.
  • the sealing plug 29 is located between the nozzle adapter 27 and a gun body extension 30 for sealing a liquid flow passage which extends through the gun to the nozzle insert 26.
  • a nozzle retaining nut 31 is threaded onto the gun body extension 30 to secure the nozzle support ring 28 in place on the gun body extension.
  • a central bore 32 extends axially through the gun body extension 30 and the gun body 11 into communication with the hose 14 through which coating liquid under high pressure is supplied to the gun.
  • a conventional valving mechanism (not shown) is mounted within the central bore 32 rearwardly of the plug 29 and is operated by the trigger 13 to control the flow of liquid through the central bore 32.
  • the forward end of the central bore 32 communicates with an axial bore 33 which extends through the plug 29, and which is aligned with rhe central bore 32.
  • the plug bore 33 is in turn aligned with a bore 34 which extends axially through the adapter 27 within which is received the nozzle insert 26.
  • the nozzle insert 26 has an axial passageway 35 terminating at an atomizing orifice 36.
  • the sealing plug 29 includes a fluid flow restriction 37 to break up laminar flow of liquid coating material to the nozzle to produce a turbulent flow.
  • This turbulent flow eliminates undesirable "tails" which might otherwise be formed on the edges of the pattern of liquid emerging from the nozzle orifice 36.
  • a channel 40 in the gun body extension 30 serves as a pressure relief channel to relieve any pressure build-up which might occur, such as in the event of a plugged nozzle.
  • the high voltage electrostatic charging electrode 20 terminates at its rearward end in a loop 41 which is snap-fit around the circumference of the sealing plug 29.
  • the high voltage power supply 18 is coupled through the cable 19 and a series of resistors (not shown) in the gun 10, the last resistor in the series being the resistor 42. The power supply 18 is thereby coupled through the series resistances including the resistor 42 to the electrode 20 via the electrode coil 41.
  • each resistive thread has a first end in electrical contact with the nozzle adapter 27 and a second, exposed end below and outward from the nozzle adapter.
  • each resistive thread such as the resistive thread 46
  • each resistive thread 46, 47 is positioned in the nozzle support ring 28 at an angle of about 45° from horizontal.
  • each of the resistive threads 46, 47 is also at an angle of about 45 0 from vertical. The resistive threads are therefore at an angle of about 90° relative to one another.
  • the outline of the reduced diameter portion 51, of the nozzle adapter 27 follows the outline of the central opening in the nozzle support ring 28 and is generally circular, having a pair of flattened vertical sides.
  • This nozzle adapter shape produces a pair of ridges extending out of the nozzle support ring at the points 48, 49 in Figure 4.
  • These ridges on the lower half of the nozzle adapter 27 provide locations along which the electrostatic field gradient is enhanced.
  • These ridges 48, 49 consequently are the most likely locations on the bottom of the nozzle tip illustrated for an arc to an electrical ground to occur.
  • the resistive threads 46, 47 With the resistive threads 46, 47 positioned as shown, extending outwardly from the ridges 48, 49, respectively, the resistive threads most effectively serve as shields for the lower portion of the nozzle tip.
  • the threads 46, 47 are each preferably a silicon carbide thread.
  • the threads 46, 47 are formed from a silicon carbide continuous fibre supplied under the name NICALON by Nippon Carbon Co., Ltd. of Tokyo, Japan.
  • each multi-strand thread is "wet" at one end by applying a small amount of a fast drying adhesive.
  • the adhesive holds the strands of the thread together, and once the adhesive has dried the thread is inserted into the ring 28 so that the rearward end of the thread extends slightly into the opening 52 in the support ring 28.
  • the bore in the support ring 28 for the thread 46 has a chamfered opening 53 in the front face 54 of the ring.
  • the adaptor 27 is inserted in the opening 52, pushing the strands of the resistive threads forwardly in the space between the adaptor 27 and the support ring 28. If the positioning of one or both of the resistive threads is such that some of the strands are pushed beyond the face 54 of the ring 28, these strands are trimmed at the face 54. After the nozzle adaptor 27 is in place, the exposed end of each of the resistive threads is trimmed so that each thread extends beyond the face 54 of the support ring about 0.030".
  • Resistive threads having various values of resistance have been utilized in guns such as the gun 10, with resistances ranging from about 15 M ohms per foot to about 200 M ohms per foot.
  • the length of each resistive thread in the support ring 28, upon completion of the illustrated nozzle assembly, is between about 3/8" and 1/2".
  • the resistance of each thread 46, 47 in the illustrated form of the invention is about 3 to 4 M ohms.

Landscapes

  • Electrostatic Spraying Apparatus (AREA)
EP85307199A 1984-10-26 1985-10-08 Druckluftlose Sprühpistole mit Entladungsschutz für die Spitze Expired EP0179593B1 (de)

Applications Claiming Priority (2)

Application Number Priority Date Filing Date Title
US06/665,028 US4611762A (en) 1984-10-26 1984-10-26 Airless spray gun having tip discharge resistance
US665028 1984-10-26

Publications (2)

Publication Number Publication Date
EP0179593A1 true EP0179593A1 (de) 1986-04-30
EP0179593B1 EP0179593B1 (de) 1988-05-11

Family

ID=24668419

Family Applications (1)

Application Number Title Priority Date Filing Date
EP85307199A Expired EP0179593B1 (de) 1984-10-26 1985-10-08 Druckluftlose Sprühpistole mit Entladungsschutz für die Spitze

Country Status (6)

Country Link
US (1) US4611762A (de)
EP (1) EP0179593B1 (de)
JP (1) JPS61103560A (de)
AU (1) AU566200B2 (de)
CA (1) CA1225825A (de)
DE (1) DE3562565D1 (de)

Families Citing this family (14)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US4830279A (en) * 1987-09-21 1989-05-16 Nordson Corporation Flat spray nozzle for a spray gun
US5044564A (en) * 1989-11-21 1991-09-03 Sickles James E Electrostatic spray gun
US4971257A (en) * 1989-11-27 1990-11-20 Marc Birge Electrostatic aerosol spray can assembly
US5409162A (en) * 1993-08-09 1995-04-25 Sickles; James E. Induction spray charging apparatus
AU676810B2 (en) * 1995-01-30 1997-03-20 Abb K.K. Spray gun type electrostatic painting apparatus
US5957395A (en) * 1997-10-21 1999-09-28 Illinois Tool Works Inc. Safe charging
US6460787B1 (en) * 1998-10-22 2002-10-08 Nordson Corporation Modular fluid spray gun
US6739529B2 (en) * 1999-08-06 2004-05-25 Cold Jet, Inc. Non-metallic particle blasting nozzle with static field dissipation
US6758418B2 (en) * 2001-08-07 2004-07-06 Nordson Corporation Swirl gun
DE10147858A1 (de) * 2001-09-27 2003-04-30 Itw Gema Ag Spritzbeschichtungsvorrichtung
GB0229493D0 (en) * 2002-12-18 2003-01-22 Battelle Memorial Institute Aroma dispensing device
DK1601409T3 (da) * 2003-02-07 2010-07-12 Beauty Source Ltd Selvbruningskabine
US20070017443A1 (en) * 2003-08-18 2007-01-25 Cynthia Skelton-Becker Wireless operator interface for material application system
US8474402B2 (en) * 2008-12-09 2013-07-02 Nordson Corporation Low capacitance container coating system and method

Citations (4)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US3731145A (en) * 1970-11-23 1973-05-01 Nordson Corp Electrostatic spray gun with self-contained miniaturized power pack integral therewith
GB1540529A (en) * 1976-11-09 1979-02-14 Hajtomuevek Es Festoberendeze Electrostatic spraying apparatus
DE2514117B2 (de) * 1974-04-01 1980-07-10 Ppg Industries, Inc., Pittsburgh, Pa. (V.St.A.) Vorrichtung zum elektrostatischen Aufsprühen von Überzugsmassen
US4355764A (en) * 1980-07-17 1982-10-26 Nordson Corporation Low capacitance airless spray apparatus

Family Cites Families (7)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US3859506A (en) * 1973-06-15 1975-01-07 Sola Basic Ind Inc Constant wattage heating element
US4258655A (en) * 1976-04-21 1981-03-31 Caterpillar Tractor Co. Electrostatic spray apparatus
CA1125358A (en) * 1978-06-01 1982-06-08 Ppg Industries, Inc. High potential discharge control circuit including a resistive material coated electrode for induction-charging electrostatic spraying system
SU712133A1 (ru) * 1978-06-30 1980-01-30 Научно-Исследовательский Институт Научно-Производственного Объединения "Лакокраспокрытие" Электростатический распылитель
JPS55126989A (en) * 1979-03-24 1980-10-01 Kyoto Ceramic Ceramic heater
US4443361A (en) * 1981-02-20 1984-04-17 Emerson Electric Co. Silicon carbide resistance element
JPS57192726A (en) * 1981-05-21 1982-11-26 Nippon Denso Co Ltd Pre-heating of plug of diesel engine

Patent Citations (4)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US3731145A (en) * 1970-11-23 1973-05-01 Nordson Corp Electrostatic spray gun with self-contained miniaturized power pack integral therewith
DE2514117B2 (de) * 1974-04-01 1980-07-10 Ppg Industries, Inc., Pittsburgh, Pa. (V.St.A.) Vorrichtung zum elektrostatischen Aufsprühen von Überzugsmassen
GB1540529A (en) * 1976-11-09 1979-02-14 Hajtomuevek Es Festoberendeze Electrostatic spraying apparatus
US4355764A (en) * 1980-07-17 1982-10-26 Nordson Corporation Low capacitance airless spray apparatus

Also Published As

Publication number Publication date
US4611762A (en) 1986-09-16
DE3562565D1 (en) 1988-06-16
CA1225825A (en) 1987-08-25
AU566200B2 (en) 1987-10-08
EP0179593B1 (de) 1988-05-11
AU4787885A (en) 1986-05-01
JPS61103560A (ja) 1986-05-22

Similar Documents

Publication Publication Date Title
EP0179593B1 (de) Druckluftlose Sprühpistole mit Entladungsschutz für die Spitze
US3746253A (en) Coating system
EP0379373B1 (de) Elektrostatisches Sprühbeschichtungsgerät mit Rotationszerstäuber
US4572438A (en) Airless spray gun having improved nozzle assembly and electrode circuit connections
US4335851A (en) Electrostatic spray gun
CA1082911A (en) Electrostatic spray coating apparatus
US5044564A (en) Electrostatic spray gun
US4182490A (en) Electrostatic spray gun
US4214709A (en) Electrostatic spray coating apparatus
GB1589435A (en) Electrostatic spray coating gun
US3009441A (en) Apparatus for electrostatically spray coating
US5622313A (en) Triboelectric powder spray gun with internal discharge electrode and method of powder coating
US3837573A (en) Apparatus for electrified spraying
EP0044676B1 (de) Vorrichtung mit niedriger Kapazitanz zum luftlosen Zerstäuben von Flüssigkeiten
AU603315B2 (en) Electrostatic spray gun device and cable assembly
USRE31867E (en) Electrostatic spray gun
US4995560A (en) Paint hose extension for electrostatic spray gun
US3251551A (en) Electrostatic coating system
US3692241A (en) Spray apparatus with atomization device
US4989793A (en) Indirect charging electrode for electrostatic spray guns
US3587967A (en) Spray coating apparatus
US3476319A (en) Electrostatic powder-coating apparatus
US3630442A (en) Electrostatic coating method and apparatus
EP0154416B1 (de) Pulversprühpistole
CA1164198A (en) Electrostatic spray gun

Legal Events

Date Code Title Description
PUAI Public reference made under article 153(3) epc to a published international application that has entered the european phase

Free format text: ORIGINAL CODE: 0009012

AK Designated contracting states

Kind code of ref document: A1

Designated state(s): CH DE FR GB LI SE

17P Request for examination filed

Effective date: 19860605

17Q First examination report despatched

Effective date: 19870520

GRAA (expected) grant

Free format text: ORIGINAL CODE: 0009210

AK Designated contracting states

Kind code of ref document: B1

Designated state(s): CH DE FR GB LI SE

REF Corresponds to:

Ref document number: 3562565

Country of ref document: DE

Date of ref document: 19880616

ET Fr: translation filed
PLBE No opposition filed within time limit

Free format text: ORIGINAL CODE: 0009261

STAA Information on the status of an ep patent application or granted ep patent

Free format text: STATUS: NO OPPOSITION FILED WITHIN TIME LIMIT

26N No opposition filed
PGFP Annual fee paid to national office [announced via postgrant information from national office to epo]

Ref country code: FR

Payment date: 19910911

Year of fee payment: 7

PGFP Annual fee paid to national office [announced via postgrant information from national office to epo]

Ref country code: GB

Payment date: 19910913

Year of fee payment: 7

PGFP Annual fee paid to national office [announced via postgrant information from national office to epo]

Ref country code: SE

Payment date: 19910917

Year of fee payment: 7

Ref country code: CH

Payment date: 19910917

Year of fee payment: 7

PGFP Annual fee paid to national office [announced via postgrant information from national office to epo]

Ref country code: DE

Payment date: 19910930

Year of fee payment: 7

PG25 Lapsed in a contracting state [announced via postgrant information from national office to epo]

Ref country code: GB

Effective date: 19921008

PG25 Lapsed in a contracting state [announced via postgrant information from national office to epo]

Ref country code: SE

Effective date: 19921009

PG25 Lapsed in a contracting state [announced via postgrant information from national office to epo]

Ref country code: LI

Effective date: 19921031

Ref country code: CH

Effective date: 19921031

GBPC Gb: european patent ceased through non-payment of renewal fee

Effective date: 19921008

PG25 Lapsed in a contracting state [announced via postgrant information from national office to epo]

Ref country code: FR

Effective date: 19930630

REG Reference to a national code

Ref country code: CH

Ref legal event code: PL

PG25 Lapsed in a contracting state [announced via postgrant information from national office to epo]

Ref country code: DE

Effective date: 19930701

REG Reference to a national code

Ref country code: FR

Ref legal event code: ST

EUG Se: european patent has lapsed

Ref document number: 85307199.1

Effective date: 19930510